How do chromosomes divide during anaphase?
Mitosis occurs in 4 main divisions:
Prophase, Metaphase, Anaphase and Telophase.
Chromosomes appear as long coiled structures at the beginning of prophase and appear as single-stranded. Each chromosome is actually double-stranded due to duplication of genetic material during interphase that precedes mitosis.
The chromosomes get shortened and thickened during prophase, so that each chromosome consists of two chromatids, joined at the centromere. Each chromatid is in fact a complete chromosome. The two chromatids of a chromosome are identical to each other in all respects.
The chromosomes get arranged at the equator of the spindle formed by astral rays orginating from centriole in animal cells. The centromere of each chromosome is attached to the opposite end of the spindle by contractile fibers.
The end of the metaphase and beginning of anaphase is marked by the splitting of centromere so that two chromatids (In fact complete chromosomes) start moving to the opposite pole during anaphase.
Thus the chromosomes divide at anaphase by the splitting of centromere.